The field of the invention is the production of isophorone and the invention is particularly concerned with a method for preparing 4,4,8,8,10-pentamethylbicyclo[4,4,0]-decene-(1,6)-one(2) having the general formula: ##STR2##
A C.sub.15 -ketone mixture, such as is obtained by fractionating the bottom product collecting in the production of isophorone, is selectively hydrated at 1 to 100 mbars at an approximate yield of 30%.
The state of the art of isophorone production may be ascertained by reference to the Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd Edition, Vol. 13 (1982), pages 918-922, particularly page 920 and U.S. Pat. Nos. 3,337,423 and 3,337,633, the disclosures of which are incorporated herein by reference.
U.S. Pat. No. 3,337,423 discloses a process for recovering isophorone in high yields from the organic reaction mixture obtained from the condensation of acetone to isophorone wherein said organic reaction mixture includes in addition to isophorone substantially both products having a lower boiling point than isophorone, which comprises passing such organic reaction mixture to a distillation zone having a head, distilling acetone in such distillation zone from an intermixture of such organic reaction mixture with a dilute aqueous alkali solution in a weight ratio of water to organic reaction mixture of from about 0.1 to 10:1 maintained at an elevated temperature, said aqueous alkali solution having an alkali concentration between about 0.001 and 0.1% by weight based on the water present in the aqueous alkali solution, continuously removing from the head of said zone the acetone being distilled, and continuously separately condensing the removed acetone, and recovering isophorone from the intermixture remaining.
U.S. Pat. No. 3,337,633 discloses a process for the production of isophorone from acetone in the presence of alkali, which comprises introducing acetone into a pressure distillation reaction zone, having a head and a sump, at a point intermediate the head solution having a concentration of alkali within the range between 0.02 and 0.1% by weight based on the total liquid content present into said zone at a point intermediate the head thereof and the point at which said acetone is introduced thereinto, distilling said acetone at a temperature of about 100.degree.-250.degree. C. under elevated pressure in said zone in countercurrent contact with said alkali solution between the points of introduction to form in said zone acetone condensation reaction products including isophorone, condensing to liquid form in the head of said zone the acetone being distilled, recovering from said head the condensed liquid acetone and returning a portion thereof to the head as reflux and recycling the remainder of the condensed liquid acetone and returning a portion thereof to the head as reflux and recyling the remainder of the condensed liquid acetone to said zone at said point of introduction of acetone, collecting the alkali solution and said acetone condensation reaction products including isophorone in the sump of said zone, recycling a portion of the collected alkali solution to said zone at said point of introduction of alkali solution, and recovering the condensation reaction products including isophorone from the sump of said zone.
Compound [A] is an appropriate preliminary stage in the synthesis of amines, diamines, heterocycles and a number of other substances. Furthermore it is useful as a scent. When isophorone is made by acetone-condensation, up to 10% of condensation products of higher molecular weights are produced, which presently are burnt off. There was a need therefore to separate this mixture or to react it into valuable products.